MuPDF

MuPDF is a program that can be used as an alternative to Adobe Acrobat. Indeed, it offers the ability to view PDF documents as easily as with this latter program.

Key Features

PDF reader: MuPDF's main function is to open PDF documents. That is useful for viewing PDF email attachments even if no PDF reader program such as Adobe Reader is installed on the computer.

Customizable: the user is free to adjust some settings according to his needs so as to read the PDF file in an easier and more comfortable way. Indeed, he is allowed to zoom in and out or to rotate the page at 90°.

Hotkeys: in order to make its handling easier, MuPDF allows using hotkeys for facilitating the performance of a specific action. For example, zoom in and out can be done by pressing +/- and rotating by pressing L or R keys.

Pros

The download and use of MuPDF are entirely free of charge.
The running of this software does not slow down the computer.